Field of the Invention
This invention relates to an artificial olfactory system and a method for detecting gas or vapour using the system thereof, and more particularly to fault tolerant artificial olfactory system for detecting the concentration of the gas or vapour.
Description of Related Arts
Odours are complex mixtures of chemical species contain hundreds or thousands of constituent molecules. The biological olfactory system is a remarkable sensor which has some very important characteristics. There are many olfactory cells or adorant receptors. The characterization of a scent or odour is not through a specific receptor but through the combined response of a plurality of the receptors. In effect, the sensors respond broadly to a range or class of odors rather than to a specific one. This is the opposite to the ideal gas sensor, which responds to only one gas, and provides a unique output for a selective species.
For example, reports by Hayward et al. in 1977 disclosed the detection of metabolic volatile end products from E. coli and P. mirabilis using gas-liquid chromatography. In this work, the metabolic activity of bacteria on growth media led to the production of volatile chemicals that appeared in the head space of the growth vessel and were subsequently detected using a gas-liquid chromatography detector. Since different microbes display different metabolic pathways, it became feasible to distinguish between different species by recognizing the formation of specific volatile markers using the gas-liquid chromatography detection method. The work of Hayward et al. in 1977 showed this approach to be highly effective in the identification of E. coli and P. mirabilis. The cited art successfully applied the microbial odour analysis method to the rapid diagnosis of bacteria responsible for urinary tract infections using the chromatography detector. However, the use of chromatography detector has a high consumption cost.
There have been many attempts in the past to mimic the biological olfactory system. Most of them are based on existing gas-sensor technologies and have many drawbacks. Gas sensors made from tin dioxide are typical of current technology, and several commercial “electronic noses” have been based on tin dioxide arrays. Platinum pellistor-type elements, similar to tin dioxide sensors, require a high power consumption, which interferes with portability and low power operation.
U.S. Pat. No. 5,807,701 disclosed a method for the identification of microbes using arrays of sensors that respond to the different gases or vapours that are produced by different microbes grown in nutrient media. Since different microbial species display different metabolic products, a broadly responsive array is thought to provide a good detector in order to capture sufficient information to make subsequent predictions on which species are present more accurately. The sensors in the array interact with the different products causing multiple sensor signals that are subsequently collectively analysed by pattern recognition techniques using software. By using appropriate pattern recognition technique, it becomes possible to recognize sensor patterns produced by different microbes. However, the detection system should be improved with greater sensitivity and reliability.
Accordingly, it can be seen in the prior arts that there exists a need to develop an artificial olfactory system to meet the above critical needs and challenges.